Current-controlling and static-reducing system



May 7, 1929. c. A. SPILQAGUE 1,711,658

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2,1919 4 Sheets-Sheet l f/yz 2 I Jmcs CURRENT SPACE 040165 mien/0r6/4/5/706 A. Sprayua M y 7, 1929- c. A. SPRAGUE 1,111,658

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2,1919 4 Sheets-Sheet 2 JPACF 6 wmflvr f wanna/v5 //v 60/0 MTf/VTIALf/we/vfor; 674/6006 4. Sp/wgue May 7, 1929. c, SPRAGUE 1,711,658

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2,1919 4 Sheets-Sheet 3 mm.- 04/6/7064. Sprague fly MA Zy 1929- c. A. SPRAGUE ,5

CURRENT CONTROLLING AND STATIC REDUCING SYSTEM Original Filed May 2,1919- 4 Sheets-Sheet 4 v fig 9.

Var/arm in 6nd Parent/kl Patented May 7, 1929.

UNITED sr- -rss PATENT O-FF-ICE.'

CLARENGEA... SPRAGUE, OF EAST ORANGE, NEWJERSEY, ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEWIYOBK, N. Y., A CORPORATION OF NEWYORK.

CURRENT-CONTROLLING Ann STATIC-REDUCING SYSTEM.

Original application filed May 2, 1919, Serial nafss iees, Patent No.1,477,017, dated December 11, 1923.

Divided and this application filed November 21, 1923. Serial No.676,038.

This application'is a division of application Serial No. 294,328, filedMay 2, 1919, Patent No. 1,477,017, granted December 11, 1923.

The present invention in its broad aspect relates to a method and meansfor combining the properties of a. plurality of electric dischargedevices, or their equivalents, ar-

ranged in parallel relation, tosecure a de sired resultant property. Itinvolves controlling the order and extent of operation of the dischargedevices, which may, for example, be thermionic vacuum tube devices.

. In a more specific aspect the invention relates to the reception ofrelatively weak signal energy in the presenceof large electricaldisturbances. It is particularly adapted to the reception ofelectromagnetic signal waves at radio receiving stations duringatmospheric or other disturbances, but is not limited to such use, sinceit is applicable, also,

for example, to wire orcable signaling sysmay be temporarily renderedinsensitive or.

permanently injured, or at least it may be impossible to receivethesignal during the persistence of the disturbances owing to its beingswamped by the disturbing waves. Protective devices are known forpreventr ing too large current from reaching the receiver but suchdevices wipe out the message as well as the excess current. It is anobject of the invention to prevent too large current fromreaching thereceiver, but at the same timeto permit the signal currents to bereceived.

A feature of theinvention relates to the method of and means forattenuating currents of abnormal magnitude while permitting signalcurrents to received. I

Another feature of the invention'relates to the control of asignalcurrent by the abnormal currentfor, determining one or another pathcurrents.

' Another feature of the invention relates to the modification'of thesignal currents by the disturbing currents whereby the signal currentspersist through the attenuation of the disturbing currents.

A further feature of the invention relates to the separate treatment ofthe normal signal currents and the currents received duringthefdisturbances.

Features concerned in securing the abovemention effects'relate, to theuse of discharge devices soar-ranged as to function sequentially or insteps in accordance with the magnitude of the received energ to modulatesignal waves in accordance with abnormal currents, and to controlattenuationof "the abnormal currents; and other features of the nventionWlll appear from the fol-- lowingdescription together with the draw-1ngs, of which Fig. lshows a receiving cir-' C1111} arrangementaccording to the invention;

lugs. 2 and 3 are curves explanatory of the action of the devlceof Fig.1; F ig. 1 is a modified circuit arrangement of which the' curves inFig. 5 are explanatory; Figs. 6

and 7 are other forms of circuit arrangements which the invention maytake, andv Fig. 8 illustrates a high power modulator or detector ofwhich the curves of Fig. 9 are explanatory.

Figs; 1 to 6 and the explanations in connection with them serve aspreliminary steps in the disclosure of the invention illustrated in Fig.7 which is a preferred form.

Referring to Fig. l the antenna 1 is connected through adjustableresistance 2 to rate batteries if desired. Plate battery 10 causes aspace current to flow normally be for the passage of the'signal tweenthe filament and plate of discharge device 4 through output winding 11,battery 10' and the secondary winding of couplin 8. The relation betweenthe magnitude or this space current and the potential impressed acrossthe space between filament 7 and anode 8 for a given constant filamenttemperature it auxiliary tubes 5 and 6 were the total space potential tov ry between thelimits indicated by b, a, the variations produced in thespace current by the signals would be represented by the difierencebetween the ordinates drawn at points 7) and 0.

11 a surge of current from some disturbing source should carry the spacepotential to some point (5 and maintain it there mo mentarily, thesignal variations coming in with the disturbing current would produce novariation in space current, since the saturation point of thecharacteristic curve A of the discharge device would have been passed,and hence the signals would be lost during the existence of thedisturbing current. Discharge device a will act then as a currentlimiting device, since for a given filament temperature no largercurrent can be made to flow through it than is represented by theordinate corresponding to the horizontal portion of curve A.

Electron discharge devices 5 and 6 are substantially like'dischargedevice 4 but are connected to the common space battery 10 'throughrespective resistances 12, 13 and potential sources 14 and 15. As shown,source 14 is of less potential than 15 and both sources are connected.so as to oppose the source 10, so that the normal space potential ofdischarge device 5 is less than that of discharge device d and that ofdischarge device 6 is less than either of the others. Also the amount ofresistance 13 included in the circuit may be assumed to be greater thanthe portion of resistance 12 that is used, The action of dischargedevices 5 and 6 is to permit current to flow in the common outputcircuit after the cut-off value of the discharge device 1 has beenreached. W ith a' space potential (Z for instance, a larger currentresults than is denoted by the curve A as indicated by the dotted curveB and the ordinate drawn at'rl. However, the current flowing throughdischarge device or discharge devices 5 and 6 is attenuated by the resistances 12 or 12 and 13, and the attenuation is greater the greaterthe currents, as is indicated by the general form of the curve B whichmaybe considered thecomposite characteristic of the group of paralleldischarge devices 4, 5 and 6 as a whole. A large surge of disturbingcurrent is. therefore greatly damped or reduced but the signals are notlost, since it may be assumed that saturation is not reached. 'Theeffect is graphically shown by the curves of Fig. 3, in which the rent,however, and all such excess current is attenuated by the resistance 12,or, if both discharge devices 5 and 6 are conducting current, by theresistances 12 and 13, and

,the result is that the disturbing current is reduced to some suchextent as 1s lndlcated by the curve E which it is assumed represents thewave actually transmitted to the output coil 11. It is evident that thesignal wave will also be attenuated but as long as the curve itcontinues to possess curvature, the signal currents will still bepresent and are transmitted through windings 11 and 16 to the inputcircuit of the detector 17 of familiar type and are rendered audible inthe receiver 18. A tuning condenser 19 may be used or the detectorcircuit may be made aperiodic or detuned by opening thekey 20. By thusgreatly attenuating the disturbing current this'circuit arrangementprevents a sudden large fluctuation of current from reaching the ear ofthe operator Owing to the curvature of characteristic B, Fig. 2, thedevices 4:, 5 and 6 will act in a measure as a detector. The lowfrequency signal currents thus set up in the inputcircuit of detector 17will in part reappear in the telephone receiver 18, by virtue of therepeating action of detector 17 and will, in part, act to modulate thecarrier current component, the resultant current not being effective inreproducing the signal" in the receiver 18. Circuit modifications inwhich this loss of energy does not occur will later be described.

The relative effects upon the operators ear of the currents produced bystatic disturbances and those due to signals maybe likened to the effectupon the eye of a powerful field of light superimposed upon which is asmall weak source of light. It the strong field is very intense, theeye-will be blinded and become incapable ofdiscriminating between thedifferent intensities. If, however, the intensities of both fields areTo the left of the line D for instance.

reduced in the same-proportion, there is a certain value at which thediscriminating power of the eye becomes greatest; According to the formof this invention just described, the intensity of thesignal and thestatic are reduced in about the same proportion, with a resultingincrease in the clear ness of the signal. According to other forms ofthe invention the static energy is very greatly reduced whiletheavailable signal energy is reduced a relatively small amount orisincreased.

The system of Fig. 1 which has been described in detail with referenceto a distubing wave of such character as to raise the space potentialabove that of source 1.0 would need some modification to make it equallyeliicacious in reducing disturbances of reverse sign. Circuitarrangements will now be described which are designed to reduceadisturbing current of either polarity and in which the detecting actionof the current limiting device taken into account.

Referring to Fig. 4:, in place of the twoelement discharge devices 4, 5and 6, discharge devices 21, 22 and 23 of the thermionic relay type areshown, each containing in addition to the hot filament and the anode, a.third or grid electrode 24, 25 or 26 respectively; The grid 24 isprovided with a polarizing potential source 27 to fix its normalpotential with respect to its filament 7 and its potential is indicatedas higher than that of its filament. Similarly,

by a source 28, the normal potential of grid 26 is fixed negative with"respect to its filament 7, while the potential of grid 25 is normallythe same as that of its filament 7. Source 10 provides a normalpotential clifference across the space between filament 7 and anode 8 ofeach of the discharge devices 21, 22 and 23. If the characteristiccurves of the discharge devices 21, 22 and 23 are as represented by therespective curves F, G and H, in Fig. 5, then a normal space currentwill flow through each discharge device in response to this normal spacepotential, the respective magnitudes of the space currents through theseveral discharge clevices being indicated by the length of the ordinateintercepted on the line 0 by the respective curves F, G and H.A'summation curve K obtained by adding curves F, G and H may serve asthe characteristic curve of the three discharge devices 21, 22.

and 23 in combination as shown. The zero on their characteristicscorresponding to their respective fixed potentials and theabscisszeindicate variations of grid potential from their respectivefixed grid potentials. Incoming signal waves vary the potentials of allthree grids between the limits h and k,

These signal variations produce very slight changes in the platecurrents through discharge devices 21 and 23 as shown by the relativelyflat portions of their characteristics F and H respectively, a

that are operated over between these limits, as determined'by thepotential sources '27 and 28 respectively. However, the variations ofplate current through discharge device 22, due to changes in its gridpotential between these limits it and 7c are considerable, as shown bythe curve G, and the res sultant curve K shows that in the comparativelylinear region ofthe curve K between limits it and 7c the variations inthe space current are very nearly proportional to variations in gridpotential and the discharge device 22 is acting as an amplifierh TheseVariations of plate potential as determined by the signal waves aretransmitted through the coupled windings 29 into the input oir cuit of adetector 30 of familiar type and are rendered audible in the receiver81. Thus the normal signal waves picked up by antenna 1 are amplified bydischarge device 22 in the ordinary manner, detected by detector 30 ofsome suitable form, and received at 31 practically without any efiectdue to, dis

charge devices 21 and 23. However, if a large disturbing wave carriesthe grid potential variation to such excessive value as either thatindicated at m on the one hand or n on the other hand, one. of thedischarge devices 21 or 23 comes into play. It will be noted that thecharacteristics F and II of discharge devices 21 and 23 respectively,are not so steep as the curve G and that the saturation region for thesetwo dischar e tent indicated first by m, brings the dis charge device2211p toithe point of its satu ration as seen from curve G, and hencepractically no current variations due to the signal are transmittedthrough coupling 29.

The discharge device 21 is also saturated andv therefore the signalvariations are not trans mitted by it. Discharge device 23, however, isoperating on a curved portion of its characteristic and is acting as adetector, rendering the signal variations audible in the receiver 34. Inthis case under the condition assumed, discharge devices 21 and 22areacting as current limiting devices permitting only current withinpredetermined limits to pass, while discharge device 23 detects thesignal variations and the variable currents which it transmits areattenuated by the resistance'33 before they reach receiver 34. Adisturbance in the opposite direction to the extent indicated by a wouldcause dis charge devices 22 and 23 to act as current limiters, anddischarge device 21 would now act as a detector for signal variations.The resultant attenuating effect is perhaps more clearly brought out bythe summation curve K which shows that between the limits 7t and 70,including the signal variations as before pointed out, the principalaction is that of amplification, indicated by the substantially linearportion of theicharacteristic between these limits, but that beyondthese limits in either direction the curve begins to fall off and thetotal current transmitted bears an increasingly smaller ratio to theincoming currents, but detection of the signals still continues byvirtue of the curvature still possessed by the characteristic. lVhenworlv ing over certain small ranges of curve K, signals may be audiblein both receivers. The phase shifting means 4E3 may then be adjusted toobtainthe proper phase relations. D

A generator of carrier or other high frequency may, if desired, becoupled to the circuit through coil 36 shown inductively related towindings 3, for the purpose of increasing the strength of the signal orotherwise rendering it more easily readable. A rey 37 is provided in thecircuit of the generator 35. Also a tuning condenser 38 may be throwninto or out or circuit across the secondary of windings 3 by key 39. Itmay be found desirable to render this tuned circuit non-oscillatory bythe insertion of suitable resistance. A. tuning condenser 40 is shown incircuit with the secondary of transformer 29. The small condensers 11and 42 are shown respectively in shunt to receivers 31 and 3a to by-passthe high he quency. current components. The direct current from battery10 may in any case be shunted past the indicating instrument by chokecoils in the well-known manner.

The devices thus far described are designed to reduce the effect ofdisturbing currents, while still permitting the signal cur-.

rents to be received but the signal currents are somewhat attenuated bythe current re ducing means Means will now be shown and described forreducing the disturbing current-s while still transmitting the signalcurrents strongly. This is accomplished in the particular means shown bycausing the lower frequency disturbing currents of large magnitude tocontrol amplification of the signal currents, after which both kinds ofcurrents are attenuated. Referring first to Fig. 6, the secondary of theantenna cou pling 3 is connected tothe input of a balanced amplifiercommonly known as the push-pull type. This comprises two dischargedevices' 45 and -16, the respective grids of which are connected each toa terminal of the secondary of coil 3, while their respective filaments4:9 and are connected together and to the midpoint of the saidseccurrent.

is connected to the common filament connection and through a combinationof discharge.

devices to the midpoint of said primary wlnding. The combination ofdischarge devices 1n the space current circuit as shown is the same asthat of Fig. 1 and. the identity of the various parts may be recognizedby the same reference characters as are used in Fig. 1. The action ofthis combination of discharge devices as described in connection withFig. 1 and 2 is to limit the current in their common circuit, not bycutting it oi'f definitely at a particular saturation value but at avarying rate somewhat as indicated by the dotted curve B of Fig. 2, sothat the signal current variations upon the disturbing waves are notlost. The normal potential of grids 4.17 and t8 is fixed preferablynegative by the source of potential 54 so that either device 45 or 16normally operates over that portion of its characteristic near thetransition from the lower horizontal portion to the substantially linearupwardly sloping portion. An incoming signal wave will render one grid,say 17, at any given instant, more negative than normally and since theimpedance of this discharge space is already practically a maximum, 'dueto its large normal negative potential, there will be substantially nochange in its output The same wave will at the same instant make thepotential of grid 48 less negative and therefore the impedance of itsdischarge space becomes lower, and an. output wave, depending upon theextent to which. the grid potential is changed, will result. For anincoming wave of alternating current then the discharge devices l5 and46 alternately conduct current under control of the input waves. Thetransmission of space current under control of signal current, while itmay be regulated to be normally adequate for the reception of signals,is less favorable than if either discharge device 45 or 4.6 wereoperating over, a more nearly linear and central portion of itscharacteristic. duced in one or theqother discharge device 45 or 16 by asuifieiently large disturbing wave of relatively low frequency, sincethe potential of one or the other grid will be raised momentarily. Thecorresponding lowering of the potential of the other grid will cause nofurther increase in the already practically maximum impedance of itsdischarge space, and transmission of signal current will be through thedischarge de- This more favorable condition is pro-v vice which has amomentarily higher grid potential than normal. In other words, thesignal currents are modulated in accordance with the lower frequencydisturbing waves, and the signals become stronger the stronger is thedisturbing current. As inthe case of the arrangement of Fig. 1 thedischarge device l transmits the normal signal currents,

- but larger currents than normal begin to 5 and 6 and become attenuatedby the 'refind their way through the discharge devices sistances 12 and13 so that all variable currents ,of abnormally large amplitude in the'common output of the discharge devices 15 and -16 are reduced beforethey reach the output windings 53 through which they are impressed uponthedetector 55 of familiar type by which they are rendered audiblein thereceiver 56. The signal current-s by having been previously boosted maystill be as strong as normal, although they have been attentuatedtogether with the disturbing currents.

It will be noted that in the arrangements shown, sharply tunedoscillatory circuits are avoided throughout the path of the receivedwvave's until after the waves have passed the current limiting andattenuating'means, so

that the possibility o'f'shockexcitation of a resonating "circuit-by asudden disturbance, whereby an aperiodic impulse is con-' vorted into aseries of oscillations in the resonating circuit, 1s 'ZLVOldGd; Afterthe currents have been attenuated there is less probability of thiseffect and-a tuning condenser in the detector circuit may be advan-'tageous inselectively transmitting only the signal currents. Condensers19, Fig. 1, 40 Fig. 1 and 57 Fig. "6 are indicated to be used for thispurpose if desired. Any suit- 'ableform of wave filter may, of course,be used in place of a single tuned circuit.

Referring now to Fig. 7 the antenna coupling 3 is connected to theinputcircuitof a detector 58 of familiar type by which the signals arerenderedaudible in receiver '59.

A tuning condenser '60 may be included around the coil winding byclosing key 61 if desired. A coupling-3 is also'shown, the secondary ofwhich is connected to the lnput terminals of an amplifier ofl the pushpull type similar in general to that of.-

Fig. 6. This pushpull amplifier differs from that of Fig. 6 mainly byhaving impressed upon the grids of the discharge de vices 64 and 65 alarge negative potential from battery 62. It is well known that underthis condition the electrons emitted by the filament, when heated, willbe forced back thereon and hence no currentwill flow in the platecircuit. This condition w1ll be unaiie-cted by small potentialvariations impressed. on the grid by normal signals.

received by the antenna system.

The negative potential of the grids of output of the amplifier.

tionas a power oscillator.

devices 64and' 65 is so adjusted that the normal currents aretransmitted by the detector 58 and the disturbing currents, if of suchlarge value as to exceed the cut-off value of the detector 58 whichvalue may be suitably predetermined, will change-the potential ofthe'grids 64 and 65 of the push-pull amplifier sufficiently to enable.

one or the other side of said amplifier to transmit the signal current.The larger the disturbing current within reasonable limits, the greaterwill be theamplification of the signal currents as explained inconnection with Fig. 6 and the signal currents are thus so augmentedthat the signals are still strong after the currents have passed thelarge attenuating resistance 66 inthe ings 63 and 67 the output wavesare impressed on the input circuitof detector 68 by which they arerendered audible in receiver 59. A. tuning condenser69 is shown whichmaybe connected across the coil 67 by closing the key 70-if desired.

Fig. 8 discloses a modulator similar to that of Fig. 7 with the additionof tubes '81 to '85 having the required grid potentials By means ofwindand output resistances to give the operatmg characteristics"shown inFig. 9, the

'chzwacteristics of tubes 65, 80, 82 and 84 being respectively the sameas those of tubes 64, 81, 83 and 85. The'source ofelectromotive force62iis of such value, as in Fig.

7, as to normallypreventfiow of space current. The two groups of tubestherefore motive force reverses in 1 direction. The

either group beginning with 64cor 65, are

shown at R, S, T and V respectively, Fig.

act alternately as the impressed electro,

operating characteristics of thet'ubes of" i 9, and W is thecharacteristic of thecombination. It will be noted that the curve 'W'maybe made substantially parabolic over a relatively very wide operatingrange and that this modulat ng system lstherefore "well ada-p tediforpowerfulmcurrents. The

system may also be used as a detector, and

with proper feed-back circuits, will func- The necessary coupling may beobtained by inductively ord can always be obtained without oblit--erating the signal.

115 relating coils 63 to coils 86, for example.

, a receiving WVhile the invention has been illustrated and describedwith particular reference to circuit for electromagnetic waves, it isnot to be limited to such a system sinceit is evident that the antenna 1may be equally well considered as the terminal of a wire line. Also theparticular discharge devices illustrated are not to be considered aslimiting the invention nor are the relations set out inthe variouscurves that have been given to be considered as liinitingthe inventionbut merely as illus-'.

trative oi principles involved and as aids to a disclosure of theinvention. Nor is the invention to be limited in other respects by thespecific embodiments shown as a whole or to the particular details, butonly by the scope out the appended claims.

What is claimed is: V r

1. The method of signaling in the presence of. a disturbing currentwhich comprises automatically increasing the amplification of the signalcurrent as the disturbing current increases and attenuating theresultant current.

2. The method of receiving signal currents in the presence of abnormalcurrents which comprises automatically reinforcing 'said signal currentsas the strength of the abnormal currents increases and then causing allsaid currentsto be attenuated.

3. The method of maintaining signal currents in the presence of largeabnormal currents which comprises automatically reintorcingsaid signalcurrents as the magnitude of said abnormal currents increases.

apThe method of receiving signals by space discharge devices, eachincluding a control electrode having different values of polarizingpotentials applied thereto, to produce different degrees ofamplification, which method comprises applying such a polarizingpotential to one of said devices as to produce one degree ofamplification of received signals in the absence of disturbing energy,and applying polarizing potentials to others of said devices such thatunder control of received disturbing energy a.

higher degree of amplification for thereceived signals is effected.

5. In a signal receiving circuit, a signal energy absorber, a receiverand two parallel current paths between said energy absorber andsaidreceiver, one of said paths contaming a detector and the other of saidpaths.

said energy absorber comprising two 'discharge devices, each having acathode, an anode and an impedance controlling electrode, said cathodeshaving a common connection andsaid impedance controlling electrodesbeing connected to said common connection in opposite sense relative tothe coupling with said energy absorber, a receiver, meansfor connectingsaid receiver to said anodes, a source of potential connected to saidcommon connection and to said means, and a current-limiting andattenuating means connected between said source of potential and saidmeans.

8. A current limiting circuit comprising a plurality of space dischargedevices, a common source of space current for said devices, anattenuator included in the space current path, means for applying tothe.

grids of said space discharge devices a biasing potential'of such valuethat space current is normally prevented from flowing therethrough andmeans for applying to said grids a potential of such value as toovercome said biasing potential whereby space current is permitted tofiow'through saidspace discharge devices. v

i In. witness whereof, I hereunto subscribe my name this 19th day ofNovember, D.

1923. I V CLARENCE ALSPRAGUE.

